New interpretation of the doping and temperature dependence of photoemission line shape and its implication to the high-T c superconductivity

Abstract

ABSTRACT Recent findings in the experiments on high T superconductors by angle resolved photoemission are discussed.Detailed temperature and doping dependent lineshape studies on cuprates lead to a new interpretation of the pho- toemission data. The broad photoemission peaks which often extend to the Fermi level when they are a few hundred meV away from the Fermi level are not single states with very large broadening. Rather, the broad structure shouldbe interpreted as a collection of states. It is found that the low energy part of this structure is involved in the pairingand, contrary to the conventional supercondutors, the pairing occurs not only near the so called Fermi surface but also away from it. Keywords: Photoemission, ARPES, Lineshape, HTSC 1. INTRODUCTION Angle resolved photoemission spectroscopy (ARPES) has played a vital role in understanding the electronic structure of the high T superconductors (HTSCs). Its contribution can be found in the band structure mapping, mappingof the Fermi surface, and gap measurement of both superconducting- and pseudo-gaps2'3. Even though manystudies on the HTSCs show very unconventional properties, the interpretations of these experimental findings havebeen mostly, to a certain extent, based on the conventional picture. Probable reason for this may be that all thesemeasured quantities are in one way or another related to the conventional BCS theory based on the band picture.